Improvement of survival from hemorrhagic shock by enterectomy in rats: finding to implicate the role of the gut for irreversibility of hemorrhagic shock

Autodigestion: Proteolytic Degradation and Multiple Organ Failure in Shock

There is currently no effective treatment for multiorgan failure following shock other than supportive care. A better understanding of the pathogenesis of these sequelae to shock is required. The intestine plays a central role in multiorgan failure. It was previously suggested that bacteria and their toxins are responsible for the organ failure seen in circulatory shock, but clinical trials in septic patients have not confirmed this hypothesis. Instead, we review here evidence that the digestive enzymes, synthesized in the pancreas and discharged into the small intestine as requirement for normal digestion, may play a role in multiorgan failure. These powerful enzymes are nonspecific, highly concentrated, and fully activated in the lumen of the intestine. During normal digestion they are compartmentalized in the lumen of the intestine by the mucosal epithelial barrier. However, if this barrier becomes permeable, e.g. in an ischemic state, the digestive enzymes escape into the wall of the intestine. They digest tissues in the mucosa and generate small molecular weight cytotoxic fragments such as unbound free fatty acids. Digestive enzymes may also escape into the systemic circulation and activate other degrading proteases. These proteases have the ability to clip the ectodomain of surface receptors and compromise their function, for example cleaving the insulin receptor causing insulin resistance. The combination of digestive enzymes and cytotoxic fragments leaking into the central circulation causes cell and organ dysfunction, and ultimately may lead to complete organ failure and death. We summarize current evidence suggesting that enteral blockade of digestive enzymes inside the lumen of the intestine may serve to reduce acute cell and organ damage and improve survival in experimental shock.

Effects of acute ethanol gavage on intestinal integrity after hemorrhage/resuscitation

BACKGROUND

In hemorrhagic shock with subsequent resuscitation (H/R), increased pro-inflammatory changes contribute to tissue injury and mortality in rodent models. Ethanol (EtOH) is assumed to modulate the inflammatory response and the subsequent organ injury after H/R. Therefore, we determined the contribution of acute ethanol gavage on intestinal inflammation and injury as well as survival after H/R in rats.

METHODS

Fourteen hours before H/R, female LEWIS rats were gavaged with single dose of EtOH or saline (5 g/kg, 30% EtOH, H/R_EtOH group or H/R_ctrl group). Then, rats were hemorrhaged to a mean arterial blood pressure of 30 ± 2 mmHg for 60 min and resuscitated. Control groups underwent surgical procedures and gavage without H/R (sham_ctrl group and sham_EtOH group). Tissue was harvested 2 h after resuscitation. Mortality was assessed 72 h after H/R.

RESULTS

Ethanol gavage increased survival after H/R from 20% to 80%, but amplified plasma alanineaminotransferase (ALT) release compared to saline gavage (2847 ± 406 vs. 1159 ± 200 IU/L, p < 0.05). Intestinal mucosal damage index, intestinal permeability, ileal myeloperoxidase levels as indicators of polymorphonuclear leukocyte (PMNL) infiltration and systemic IL-6 levels as well as ileal IL-6 and TNF gene expressions after H/R were reduced and partly restored after ethanol gavage when compared to the saline gavaged group after H/R.

CONCLUSIONS

Taken together, we propose that acute ethanol gavage prior to H/R 1) did not enhance intestinal mucosa injury after H/R and 2) suppressed the H/R-induced inflammatory response. Both findings seem to contribute to the ethanol-induced survival benefit after H/R in our model.

2008 Landis Award lecture. Inflammation and the autodigestion hypothesis

Although long recognized in microvascular research, an increasing body of evidence suggests that inflammatory markers are present in human diseases. Since the inflammatory cascade serves as a repair mechanism, the presence of inflammatory markers in patient groups has raised an important question about the mechanisms that initiate the inflammatory cascade (i.e., the mechanisms that cause tissue injury). Using a severe form of inflammation, shock, and multiorgan failure, for which there is no accepted injury mechanism, we summarize studies that suggest that the powerful pancreatic digestive enzymes play a central role in the destruction of the intestine and other tissues if their compartmentalization in the lumen of the intestine and in the pancreas is compromised. Further, we summarize evidence that uncontrolled degrading enzyme activity in plasma causes proteolytic cleavage of the extracellular domain of membrane receptors and loss of associated cell functions. For example, in a model of metabolic disease with type II diabetes, proteolytic cleavage of the insulin receptor causes the inability of insulin to signal glucose transport across membranes. The evidence suggests that uncontrolled proteolytic and lipolytic enzyme activity may trigger the mechanism for tissue injury. The significance of such mechanisms remain to be explored in human diseases.

Mesenteric lymph duct ligation improves survival in a lethal shock model. Shock. 2008;30:680-685. [PMID: 18496238 DOI: 10.1097/shk.0b013e318173edd1]

The goal of this study was to test the hypothesis that factors released from the gut and carried in the mesenteric lymph contribute to mortality in a lethal gut I/R model. To test this hypothesis, a lethal splanchnic artery occlusion (SAO) shock model was used in male Sprague-Dawley rats. In the first set of experiments, ligation of the mesenteric lymph duct (LDL), which prevents gut-derived factors carried in the intestinal lymphatics from reaching the systemic circulation, significantly improved 24-h survival after a 20-min SAO insult (0% vs. 60% survival; P < 0.05). This increase in survival in the LDL-treated rats was associated with a blunted hypotensive response. Because increased iNOS-induced NO levels have been implicated in SAO-induced shock, we measured plasma nitrite/nitrate levels and liver iNOS protein levels in a second group of animals. Ligation of the mesenteric lymph duct significantly abrogated the SAO-induced increase in plasma nitrite/nitrate levels and the induction of hepatic iNOS (P < 0.05). In an additional series of studies, we documented that LDL increased not only 24-h but also long-term 7-day survival. During the course of these studies, we made the unexpected finding that Sprague-Dawley rats from different animal vendors had differential resistance to SAO, and that the time of the year that the experiments were carried out also influenced the results. Nonetheless, in conclusion, these studies support the hypothesis that factors carried in the mesenteric lymph significantly contribute to the development of irreversible shock after SAO.

Hemorrhage-induced hepatic injury and hypoperfusion can be prevented by direct peritoneal resuscitation

BACKGROUND

Crystalloid fluid resuscitation after hemorrhagic shock (HS) that restores/maintains central hemodynamics often culminates in multi-system organ failure and death due to persistent/progressive splanchnic hypoperfusion and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) using peritoneal dialysis solution reverses HS-induced splanchnic hypoperfusion and improves survival. We examined HS-mediated hepatic perfusion (galactose clearance), tissue injury (histopathology), and dysfunction (liver enzymes).

METHODS

Anesthetized rats were randomly assigned (n = 8/group): (1) sham (no HS); (2) HS (40% mean arterial pressure for 60 min) plus conventional i.v. fluid resuscitation (CR; shed blood + 2 volumes saline); (3) HS + CR + 30 mL intraperitoneal (IP) DPR; or (4) HS + CR + 30 mL IP saline. Hemodynamics and hepatic blood flow were measured for 2 h after CR completion. In duplicate animals, liver and splanchnic tissues were harvested for histopathology (blinded, graded), hepatocellular function (liver enzymes), and tissue edema (wet-dry ratio).

RESULTS

Group 2 decreased liver blood flow, caused liver injuries (focal to submassive necrosis, zones 2 and 3) and tissue edema, and elevated liver enzymes (alanine aminotransferase (ALT), 149 +/- 28 microg/mL and aspartate aminotransferase (AST), 234 +/- 24 microg/mL; p < 0.05) compared to group 1 (73 +/- 9 and 119 +/- 10 microg/mL, respectively). Minimal/no injuries were observed in group 3; enzymes were normalized (ALT 89 +/- 9 microg/mL and AST 150 +/- 17 microg/mL), and tissue edema was similar to sham.

CONCLUSIONS

CR from HS restored and maintained central hemodynamics but did not restore or maintain liver perfusion and was associated with significant hepatocellular injury and dysfunction. DPR added to conventional resuscitation (blood and crystalloid) restored and maintained liver perfusion, prevented hepatocellular injury and edema, and preserved liver function.

The synergistic effect of ethanol and shock insults on Caco-2 cytokine production and apoptosis

Gut epithelial cells are important in orchestrating immunoinflammatory responses in the gut and may impact systemic immunocompetent cells after shock and trauma. Ethanol (EtOH) intoxication is an important etiological factor in trauma and may increase the likelihood of posttraumatic septic complications. Both EtOH and gut I/R impair intestinal barrier function. However, their combined effects on intestinal epithelial cell function and barrier integrity are unknown. Confluent CaCO2 cell monolayers were grown in a two-chamber culture system and exposed to 0.1% EtOH and/or Escherichia coli C-25 under normoxic (21% O2) or hypoxia (5% O2) followed by reoxygenation (H/R). Apical and basal compartment supernatants were collected, and TNF and IL-6 were quantitated by enzyme-linked immunosorbent assay (picograms per milliliter). CaCO2 cell integrity was indexed by apoptosis and monolayer permeability. TNF-alpha production by CaCO2 cells are greatest when incubated with EtOH and then exposed to H/R group. The apical levels of TNF production are consistently higher than basal levels, although the trend toward increased cytokine production is similar in both compartments. IL-6 production by the CaCO2 cell is also greatest when CaCO2 cells incubated with EtOH undergoes H/R. Lastly, the findings in apoptosis mirror the data of the TNF production in the apical compartment. Ethanol and H/R have a synergistic effect on cytokine production and barrier dysfunction in this model. They may also contribute to increased infectious complications and posttraumatic organ failure.

Hemorrhagic shock influence on colonic anastomoses in rats: evaluation of rupture by liquid distension resistance test

PURPOSE: To evaluate the effect of hemorrhagic shock in colonic anastomoses in rats, with a rupture by liquid distension resistance test. METHODS: Wistar lineage rats, averaging 90 days old and weighing from 310 to 380 grams were divided into two groups. In the first group (G1), 10 animals were submitted to colonic anastomoses in normovolemic terms and the second group (G2), of 10 animals, was submitted to colonic anastomoses in hypovolemic conditions. The shock was caused by half milliliter of blood withdrawn, every two minutes, until the value of average 50mmHg arterial pressure or a total volume corresponding 30% withdrawal of volemia was reached. Serum lactate dosages were carried out at the beginning and end of the procedure. The average serum lactate values at the end of the surgery were 1.91 mmol/l in G1 group and 3.69 mmol/l in G2 group (p<0.05). On the fifth postoperative day, the animals were euthanized. The anastomoses were evaluated with a rupture by liquid distension resistance test. RESULTS: In G1, the average value of colonic rupture was 160.7 mmHg whereas in G2 it was 152.1mmHg (p>0.05). CONCLUSION: Hemorrhagic shock, under the established conditions of this study, had no influence on colonic anastomoses in rats evaluated with the rupture by liquid distention resistance test.

Gut-lymph hypothesis of systemic inflammatory response syndrome/multiple-organ dysfunction syndrome: validating studies in a porcine model

BACKGROUND

Trauma-hemorrhagic shock (T/HS) mesenteric lymph from rats has multiple biological properties and appears to cause organ injury via the activation of neutrophils and endothelial cells. As the next step in testing the potential clinical relevance of these rodent studies, we utilized a swine T/HS model to determine whether the intestinal lymph results observed in the rodent could be replicated in swine. A porcine model was chosen because the pig and human cardiovascular and gastrointestinal physiology are similar.

METHODS

Male pigs were subjected to T/HS and a major intestinal lymph duct was cannulated. Hemorrhagic shock (mean arterial pressure, 40 mm Hg) was performed by withdrawing blood, for 3 hours or until the base deficit reached -5. Animals were then resuscitated in two stages to mimic the prehospital and hospital phases of resuscitation. Mesenteric lymph was collected hourly throughout the experiment and its biological activity was tested on neutrophils (respiratory burst) and endothelial cells (monolayer permeability and cytotoxicity).

RESULTS

T/HS lymph but not trauma-sham shock lymph (T/SS) increased neutrophil activation as reflected by an augmented respiratory burst. Likewise T/HS lymph collected at all time points up to 5 hours postshock significantly increased endothelial cell permeability by twofold or greater (p < 0.05), whereas T/HS lymph produced during the first 2 hours postshock was cytotoxic for endothelial cells (viability 70%, p < 0.05 vs. preshock). In contrast, T/SS lymph had no effect on the endothelial cells.

CONCLUSION

This large animal model validates rodent studies showing that the shock-injured gut releases biologically active factors into the mesenteric lymph and these factors activate neutrophils and injure endothelial cells.

PERITONEAL LAVAGE WITH OXYGENATED PERFLUOROCHEMICAL IMPROVES HEMODYNAMICS, INTESTINAL INJURY, AND SURVIVAL IN A RAT MODEL OF SEVERE HEMORRHAGIC SHOCK AND RESUSCITATION

Perfluorochemicals (PFC) are chemical substances that have a high solubility for oxygen. This study investigated the effect of peritoneal lavage with oxygenated PFC (O2-PFC) against hemorrhagic shock and resuscitation (HS/R). Male Sprague-Dawley rats were anesthetized and bled to a mean arterial pressure (MAP) of 30 to 35 mmHg for 120 min. The animals then were resuscitated over 20 min with an infusion of shed blood. Peritoneal lavage was performed by inflow and outflow of the PFC solution at 80 mL/h during the shock-resuscitation period. Rats were divided into four groups. Group I, HS without peritoneal lavage; Group II, HS with nitrogenated PFC (N2-PFC) lavage; Group III, HS with O2-PFC lavage; and Group IV, sham-operated rats. Seven of seven (100%) rats in Group IV and six of seven (85.7%) rats in Group III survived for 48 h, and one of seven (14.3%) rats in Group I and zero of seven rats in Group II survived (P < 0.01). In Group III rats, metabolic acidosis (assessed by blood gas analysis) and depression of intestinal blood flow (assessed by laser Doppler flowmetry) during HS were markedly ameliorated in comparison with those in Group I or Group II rats. The elevation of plasma TNF-alpha and IL-6 after HS/R were also attenuated in Group III. Histological study showed that O2-PFC lavage significantly decreased the degree of intestinal mucosal damage. We conclude that treatment with O2-PFC lavage ameliorated HS/R-induced metabolic acidosis and intestinal damage, which was associated with better mortality, possibly by preserving microvascular perfusion and maintaining oxygen metabolism.

HEMORRHAGIC SHOCK RESUSCITATION AFFECTS EARLY AND SELECTIVE MESENTERIC ARTERY ENDOTHELIAL FUNCTION THROUGH A FREE RADICAL-DEPENDENT MECHANISM

Mesenteric ischemia/reperfusion occurring during hemorrhagic shock and resuscitation (H/R) induces a systemic inflammatory response and damages endothelial cells. Our aim was to investigate whether H/R affects selectively mesenteric vascular reactivity and the roles of free radicals and inducible nitric oxide (NO) synthase (iNOS) in these changes. Rats subjected to H (30 min)/R (60 min) in the presence or absence of the free radical scavenger N-2 mercaptopropionyl glycine (MPG), or the specific inhibitor of iNOS [(3) N-(3-aminomethyl)benzyl) acetaminide; 1400W] were studied. Saline requirements to maintain systemic blood pressure during R (53.4 +/- 5.2 mL/kg/h) were reduced by MPG (26.2 +/- 3.1) and 1400W (37.5 +/- 4.1). H/R reduced maximal mesenteric arteries relaxation to acetylcholine (sham: 70% +/- 5%, H/R: 21% +/- 3%) and this impairment was prevented by MPG (66% +/- 10%) and reduced by 1400W (49% +/- 9%). H/R did not affect the endothelium-independent relaxations. Maximal responses to phenylephrine were reduced in mesenteric arteries by H/R (3.6 +/- 0.5 mN/mm vs. sham 6.5 +/- 0.5), this impairment was prevented by 1400W and MPG. No impaired response to acetylcholine was detected in skeletal muscle arteries. H/R was associated with an increased production of TNF-alpha (169 +/- 8.5 ng/mL vs. sham 38 +/- 5 ng/mL), and this was reduced to 75 +/- 8 ng/mL in MPG-treated rats. Total intestinal content of iNOS mRNA was also increased by H/R and this increase was partly reduced by treatment with MPG. H/R induces an early and selective mesenteric endothelial cell dysfunction through a mechanism that involves oxygen-derived free radicals and NO produced by iNOS. H/R is associated with a mesenteric hyporeactivity through an induction of NOS and may be prevented by scavenging free radicals. This early impairment in endothelial function is associated with a local inflammatory response.

Mild hypothermia during hemorrhagic shock in rats improves survival without significant effects on inflammatory responses

OBJECTIVE

To explore the hypothesis that the survival benefit of mild, therapeutic hypothermia during hemorrhagic shock is associated with inhibition of lipid peroxidation and the acute inflammatory response.

DESIGN

Prospective and randomized.

SETTING

Animal research facility.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent pressure-controlled (mean arterial pressure 40 mm Hg) hemorrhagic shock for 90 mins. They were randomized to normothermia (38.0 +/- 0.5 degrees C) or mild hypothermia (33-34 degrees C from hemorrhagic shock 20 mins to resuscitation time 12 hrs). Rats were killed at resuscitation time 3 or 24 hrs.

MEASUREMENTS AND MAIN RESULTS

All seven rats in the hypothermia group and seven of 15 rats in the normothermia group survived to 24 hrs (p <.05). Hypothermic rats had lower serum potassium and higher blood glucose concentrations at 90 mins of hemorrhagic shock (p <.05). At resuscitation time 24 hrs, the hypothermia group had less liver injury (based on serum concentrations of ornithine carbamolytransferase and liver histology) and higher blood glucose than the normothermia group (p <.05). There were no differences in serum free 8-isoprostane (a marker of lipid peroxidation by free radicals) between the two groups at either baseline or resuscitation time 1 hr. Serum concentrations of interleukin- 1 beta, interleukin-6, and tumor necrosis factor-alpha peaked at resuscitation time 1 hr. Tumor necrosis factor-alpha concentrations were higher (p <.05) at resuscitation time 1 hr in the hypothermia group compared with the normothermic group. Serum cytokine concentrations were not different between survivors and nonsurvivors in the normothermia group. Serum cytokine concentrations returned to baseline values in both groups by 24 hrs. There were no differences in the number of neutrophils in the lungs or the small intestine between the groups. More neutrophils were found in the lungs at resuscitation time 3 hrs than at resuscitation time 24 hrs in both groups (p <.01).

CONCLUSIONS

These data suggest that lipid peroxidation and systemic inflammatory responses to hemorrhagic shock are minimally influenced by mild hypothermia, although liver injury is mitigated and survival improved. Other mechanisms of benefit from mild hypothermia need to be explored.

Systemic hypothermia, but not regional gut hypothermia, improves survival from prolonged hemorrhagic shock in rats

BACKGROUND

Extracorporeal blood perfusion of the gut or enterectomy can improve survival during hemorrhagic shock (HS), suggesting that the gut may be of primary importance in resuscitation. We hypothesized that cooling the gut alone could improve survival in a rat HS model and avoid potential deleterious effects of systemic hypothermia.

METHODS

Thirty-two Sprague-Dawley rats were anesthetized with halothane. The gut (small intestine, cecum, and colon) was exteriorized. The right atrial (T ), rectal, and gut (T ) intraluminal temperatures were monitored. HS was induced by withdrawal of 2 mL of blood per 100 g body weight over 10 minutes. Mean arterial pressure was then maintained at 35 to 40 mm Hg to HS 90 min. From HS 20 min to resuscitation time 1 h, rats were randomized into four groups (n = 8 each): normothermia (T and T approximately 38.0 degrees C), gut-25 degrees C (T approximately 38 degrees C, T approximately 25 degrees C, induced by rinsing the gut with cooled saline), gut-33 degrees C (T approximately 38 degrees C, T approximately 33 degrees C), and systemic hypothermia (T approximately 33 degrees C, T approximately 25 degrees C). At HS 90 min, shed blood and Ringer's solution were infused to restore normotension. Survival, metabolism, and tissue damage were observed to 72 hours.

RESULTS

Blood pressure was not different between groups. Compared with the normothermia group, the systemic hypothermia group had lower base deficit and lactate, and needed less fluid during resuscitation for normotension (p < 0.05), but these values were not different in the gut hypothermia groups. In addition, there were no significant improvements in tissue protection induced by regional gut hypothermia, whereas the systemic hypothermia group had lower plasma potassium, lower ornithine carbamoyltransferase (marker of liver injury), and higher glucose levels after HS (all p < 0.05). All rats in the systemic hypothermia group survived to 72 hours, whereas there was only one survivor in the normothermia group, two in the gut-33 degrees C group, and none in the gut-25 degrees C group (all p < 0.05 vs. systemic hypothermia).

CONCLUSION

Cooling the gut alone does not improve acute survival from HS, suggesting that early deaths are not secondary to gut ischemia. Mild systemic hypothermia allowed 100% survival from prolonged HS.

Intestinal preconditioning prevents systemic inflammatory response in hemorrhagic shock. Role of HO-1

Intestinal ischemia-reperfusion has been implicated in the systemic inflammatory response and organ injury in hemorrhagic shock, but the exact role of the intestine has never been directly demonstrated. Preconditioning (PC) with brief periods of intermittent ischemia is a known potent anti-ischemic intervention and thus can be used as a tool to assess the role of local intestinal ischemia-reperfusion injury in systemic inflammatory response. Thus rats were first subjected to sham surgery or intestinal preconditioning with four cycles of 1-min ischemia and 10 min of reperfusion 24 h before hemorrhagic shock followed by resuscitation. PC reduced fluid requirements, lung edema, and lactate and tumor necrosis factor-alpha production. These effects were abolished by the heme-oxygenase-1 (HO-1) inhibitor tin protoporphyrin (Sn-PP). PC induced more than fivefold in intestinal HO-1 expression. These results suggest that intestinal ischemia-reperfusion is a major trigger for inflammatory response and organ injury in nonseptic shock. HO-1 appears to play an important role in the protective effect of intestinal preconditioning.

Protease inhibition in the intestinal lumen: attenuation of systemic inflammation and early indicators of multiple organ failure in shock

Our recent evidence suggests that pancreatic digestive enzymes in the lumen of the intestine may play a major role in the production of cardiovascular stimulatory factors during splachnic artery occlusion and reperfusion. These stimulators are detected in plasma, but their origin and mechanism of production has remained uncertain. We examine here in the rat the role of pancreatic enzymes with and without administration of a serine protease inhibitor (FOY) into the lumen of the small intestine during splanchnic artery occlusion (90 min) and reperfusion (120 min). In the presence of pancreatic enzyme inhibition in the lumen of the intestine, there is significantly enhanced survival rate, lower levels of inflammatory mediator production, the femoral artery blood pressure is maintained close to control levels, and there are significantly lower levels of cell activators in plasma. These results support the hypothesis that pancreatic enzymes may escape across the brush border barrier during intestinal ischemia and thereby initiate the production of a powerful set of cytotoxic mediators. Blockade of pancreatic enzymes in the lumen of the intestine may be a tool to interfere with inflammation and early indicators of multiorgan failure.

Peritoneal ventilation with oxygen improves outcome after hemorrhagic shock in rats

OBJECTIVE

In experimental pulmonary consolidation with hypoxemia in rabbits, peritoneal ventilation (PV) with 100% oxygen (PV-O2) improved PaO2. We hypothesized that PV-O2 could improve outcome after hemorrhagic shock (HS) with normal lungs, by mitigating dysoxia of the abdominal viscera.

DESIGN

Randomized, controlled, laboratory animal study.

SETTING

University animal research facility.

SUBJECTIVE

Male Sprague-Dawley rats.

INTERVENTIONS

Thirty rats under light anesthesia (N2O/oxygen plus halothane) and spontaneous breathing underwent blood withdrawal of 3 mL/100 g over 15 mins. After volume-controlled HS phase 1 of 60 mins, resuscitation phase 2 of 60 mins included infusion of shed blood and, if necessary, additional lactated Ringer's solution intravenously to control normotension from 60 to 120 mins. This was followed by observation phase 3 for 7 days. We randomized three groups of ten rats each: group I received PV-O2, starting at 15 mins of HS at a rate of 40 inflations/min, and a peritoneal "tidal volume" of 6 mL, until the end of phase 2. Group II received the same PV with room air (PV-Air). Control group III was treated without PV.

MEASUREMENTS AND MAIN RESULTS

During the second half of HS phase 1, mean arterial pressures were higher in the PV-O2 group I compared with the PV-Air group II and control group III (p < .05). All 30 rats survived the 120 mins of phases 1 and 2. Survival to 7 days was achieved by ten of ten rats in PV-O2 group I; by nine of ten in PV-Air group II; and by five of ten in control group III (p < .05 vs. group I; NS vs. group II). Survival times of <7 days were 5 days in the one death of group II and ranged between 6 hrs and 4 days in the five deaths of group III. In 7-day survivors, neurologic deficit scores (0% to 10% = normal, 100% = death) were normal, ranging between zero and 8%. Necropsies of rats that died during phase 3 showed multiple areas of necrosis of the gut, some with perforations. Necropsies in the five survivors to 7 days of group III showed marked macroscopic and microscopic changes (scattered areas of necrosis of stomach and intestine, adhesions, and pale areas in the liver). These changes were absent or less severe in the nine survivors of group II. Viscera appeared normal in all ten rats of PV-O2 group I.

CONCLUSIONS

Peritoneal ventilation with oxygen during and after severe hemorrhagic shock in rats seems to decrease morbidity and mortality by helping preserve viability of abdominal viscera.

The important role of the gut in initiating the hyperdynamic response during early sepsis

BACKGROUND

Although the initial response to sepsis includes a hyperdynamic phase and although the increased hepatic perfusion in early sepsis is due solely to the increased portal blood flow, it remains unknown whether the gut plays an important role in producing such a response.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats underwent a complete enterectomy (ER) before being subjected to sepsis by cecal ligation and puncture (CLP; the cecum was excised from the removed gut and stitched to the posterior peritoneum in ER groups) or sham operation. At 2 h after CLP (i.e., the early, hyperdynamic phase of sepsis), cardiac output and heart performance (+/-dP/dt(max)), as well as hepatic and renal blood flow, were measured. Systemic and regional oxygen delivery (DO(2)) and oxygen consumption (VO(2)) were also determined.

RESULTS

Cardiac output, heart performance, organ blood flow, as well as DO(2) and VO(2), increased significantly 2 h after CLP. ER prior to the onset of sepsis, however, prevented the elevation of those parameters. ER in sham animals did not alter the measured parameters with the exception that portal blood flow decreased by 85% and hepatic arterial blood flow increased by 368%, resulting in no significant reduction in hepatic DO(2) and VO(2). There were no changes in circulating blood volume among groups, indicating that the effect of ER on hemodynamics after CLP was not due to alterations in blood volume.

CONCLUSION

Since ER immediately before the onset of sepsis prevents the increase in cardiac output and regional hemodynamics, the gut appears to play an important role in producing the hyperdynamic response during the early stage of polymicrobial sepsis.

Generation of in vivo activating factors in the ischemic intestine by pancreatic enzymes

One of the early events in physiological shock is the generation of activators for leukocytes, endothelial cells, and other cells in the cardiovascular system. The mechanism by which these activators are produced has remained unresolved. We examine here the hypothesis that pancreatic digestive enzymes in the ischemic intestine may be involved in the generation of activators during intestinal ischemia. The lumen of the small intestine of rats was continuously perfused with saline containing a broadly acting pancreatic enzyme inhibitor (6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfate, 0.37 mM) before and during ischemia of the small intestine by splanchnic artery occlusion. This procedure inhibited activation of circulating leukocytes during occlusion and reperfusion. It also prevented the appearance of activators in portal venous and systemic artery plasma and attenuated initiating symptoms of multiple organ injury in shock. Intestinal tissue produces only low levels of activators in the absence of pancreatic enzymes, whereas in the presence of enzymes, activators are produced in a concentration- and time-dependent fashion. The results indicate that pancreatic digestive enzymes in the ischemic intestine serve as an important source for cell activation and inflammation, as well as multiple organ failure.

Time course of endothelial-neutrophil interaction in splanchnic artery ischemia-reperfusion

Splanchnic artery occlusion and reperfusion (SAO/R) results in a severe form of circulatory shock that has a high mortality rate. To examine the time course of the early events involved in SAO/R, occlusion of the superior mesenteric artery (SMA) and the celiac artery (120 min) were followed by reperfusion periods of 0, 2.5, 5, 20, 30, 60, or 120 min. Relaxation of isolated SMA vascular rings to the endothelium-dependent vasodilator ACh was unimpaired following 120 min of ischemia (86 +/- 5%); however, significant (P < 0.01) reductions in endothelium-dependent vasorelaxation were observed following 2.5 min (53 +/- 6%) of reperfusion with severe dysfunction (P < 0.001) observed at 20 min (29 +/- 4%). Neutrophil adherence to the endothelium increased as a function of reperfusion time with a 2.3-fold increase observed at 20 min (P < 0.01) and a 3.4-fold increase observed at 120 min (P < 0.001). Intestinal myeloperoxidase activity was significantly increased 30 min after reperfusion (P < 0.05), whereas surface expression of P-selectin progressively increased at 5 (P < 0.05) and 30 min (P < 0.001) postreperfusion. These findings demonstrate that endothelial dysfunction is a very early event in the pathophysiology of SAO/R, subsequently resulting in increased surface expression of P-selectin and the adherence of neutrophils to the endothelium that leads to neutrophil accumulation in the splanchnic viscera.

Is gut the "motor" for producing hepatocellular dysfunction after trauma and hemorrhagic shock?

BACKGROUND

Although studies suggest that the gut may be the "motor" responsible for producing sepsis and multiple organ failure after injury, it is not known whether enterectomy prior to the onset of hemorrhage alters proinflammatory cytokines TNF and IL-6 and, if so, whether hepatocellular dysfunction and damage are prevented or attenuated under such conditions.

MATERIALS AND METHODS

Under methoxyflurane anesthesia, an enterectomy in the rat was performed by excision of the duodenum, jejunum, and ileum. The rats were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximal shed volume was returned in the form of Ringer's lactate. The animals were then resuscitated with four times the volume of shed blood with Ringer's lactate over 1 h. At 1.5 h after the completion of resuscitation, hepatocellular function [i.e., the maximal velocity (Vmax) and transport efficiency (Km) of indocyanine green (ICG) clearance] was assessed by an in vivo ICG clearance technique. Blood samples were taken for the measurement of TNF, IL-6, and liver enzymes (i.e., SGPT and SGOT). Cardiac output and microvascular blood flow were determined by ICG dilution and laser Doppler flowmetry, respectively.

RESULTS

The increase in circulating levels of TNF but not IL-6 was prevented by enterectomy prior to hemorrhage. The reduced Vmax and K(m) and elevated SGPT and SGOT following hemorrhage and resuscitation, however, were not significantly affected by prior enterectomy. Moreover, enterectomy before hemorrhage further reduced hepatic perfusion.

CONCLUSION

Since enterectomy prior to the onset of hemorrhage does not prevent or attenuate the reduced ICG clearance and elevated liver enzymes despite downregulation of TNF production, it appears that the small intestine does not play a significant role in producing hepatocellular dysfunction and injury following trauma and hemorrhagic shock.